<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>

		<p id="demo">史太帅</p>

		<button onclick="myFunction()">点我<tton>
				<h2 class="example">韦德</h2>

				<button onclick="myFunction1()">点我<tton>

						<p class="example">哈哈哈哈哈</p>
						<button onclick="myFunction2()">点我<tton>
								<script>
									function myFunction() {
										document.querySelector("#demo").innerHTML = "真特么帅";
									}

									function myFunction1() {
										document.querySelector(".example").style.backgroundColor = "green";
									}

									function myFunction2() {
										document.querySelector("p.example").style.backgroundColor = "red";
									}
								</script>
								</script>

	</body>
</html>
